This invention relates to an apparatus for abating the noise from an axial blower.
Despite its small size and light weight, the axial blower enjoys high operational efficiency and is capable of delivering large volumes of air as compared with other types of blowers and, therefore, finds favorable acceptance for use in removal of foul air from buildings and ships, in ventilation of mining pits and shafts, etc. The axial blower, however, has a shortcoming that it emits a loud noise because the blades of the rotor are operated at an unusually high peripheral speed compared with other types of blowers. The simplest way of abating the loud noise of the axial blower would be by increasing the diameter of the blower's rotor blade and thereby decreasing proportionally the peripheral speed of the blades in providing a required draft of air. Though capable of repressing the generation of loud noise without any degradation of the blower's operational efficiency, this method nevertheless proves disadvantageous in the respect that the blower size will inevitably be increased in most cases to the extent of jeopardizing its economical feasibility. There has been suggested a method for abating the noise of the blower by having a proper noise absorber disposed on the inlet side or discharge side of the duct of the axial blower. This method has a disadvantage that the noise absorber reduces the operational efficiency of the blower and the noise-abating effect aimed at is not so conspicuous as might be expected because the current of air in motion flows partly through the noise absorber as well. There has also been suggested a method for repressing the generated noise by suitably changing the angle of inclination and/or direction of the rotor blades attached to the rotary shaft of the blower and of the stationary blades attached to the casing.
An object of the present invention is to provide an apparatus for abating the noise of the axial blower effectively without giving any modification to the axial blower in itself, providing the axial blower with any specific auxiliary device such as a noise absorber or entailing any reduction in the operational efficiency of the axial blower.